This is definitely the not the most straight forward clue.
As a highly visual person, I found the last picture, where the ruler is on top of a completed unit, the most helpful in understanding it all. An important thing is that the lines of the ruler run along the length-wise or width-wise grain of the fabric. Two of the edges of the completed unit have bias edges. (And the half-square triangle that was the first component of this unit has bias edges on the outside of itself, and its diagonal seam is on the grain.)
Bonnie says there is more to come for this unit, so expect that that the bias edges will be joined with the bias edges on some other (future?) component. Or possibly, these triangles will be used as setting triangles.